Reversing valves are typically used in various systems in which a fluid is directed to flow in various alternative loops or circuits. For instance, heat pumps are specialized refrigeration systems that can be selectively configured to operate in either of two different modes. In the first, or cooling mode, energy in the form of heat is removed from an “inside” environment and transferred to an “outside” environment. Accordingly, in the second, or heating mode, heat energy is transferred into the inside environment. To carry the heat energy, the heat pump system uses a compressor to circulate fluid refrigerant through a closed system that includes heat transfer coils located in each environment. In addition to circulating the refrigerant, the compressor is used to impart heat into the system.
To switch the heat pump system between heating and cooling modes, the system uses a reversing valve assembly that can be selectively manipulated to alter the flow of refrigerant. The reversing valve assembly typically includes a valve body having at least four ports through which the reversing valve assembly is interconnected with the rest of the heat pump system. The first port is always in communication with the high pressure discharge of the compressor while the second port is always in communication with the low pressure inlet of the compressor. The remaining two ports, or system ports, are in communication with the heat transfer coils. By using the reversing valve assembly to change the direction of refrigerant flow between the heat transfer coils, the heat pump system is switched between heating and cooling modes.
To change the direction of refrigerant flow, the reversing valve assembly also includes a movable valve member that can be selectively placed between one of two alternative positions. In the first position, the valve member channels refrigerant directly between the second, compressor inlet port and one of the system ports while in the second position, the valve member channels refrigerant directly between a compressor inlet port and the other system port. Often, in prior art reversing valves, the valve member is moved in response to a change in an actuating pressure that is supplied from a pilot valve assembly. The pilot valve assembly is an electrically-operated device that is in fluid communication with both the valve body and the heat pump system. The pilot valve assembly draws refrigerant pressure from the system and converts that pressure to the actuating pressure which is then directed onto the valve body to urge the valve member between positions. Drawbacks associated with the use of pilot valve assemblies to supply an actuating pressure include the additional parts and complex fluid piping and sealing arrangements that are required.
In addition to channeling the refrigerant between the compressor inlet port and either of the system ports, the valve member also functions to prevent the high pressure refrigerant from the compressor discharge port from directly entering the compressor inlet port. Because the valve member is subject to the large pressure differential existing between the compressor discharge port and the compressor inlet port, prior art valve members are often provided with additional support structures. These support structures are typically located proximate to where the valve member encounters the second, compressor inlet port and may obstruct refrigerant flow resulting in an increase in the pressure drop across the reversing valve. Since the compressor must make up for the pressure drop, the overall efficiency of the heat pump system suffers.
By design, in prior art reversing valves assemblies, the compressor inlet port and two system ports are typically arranged adjacent to each other. Accordingly, to redirect refrigerant flow between any selected pairing of the compressor inlet port and the two system ports, the valve member must channel refrigerant through a relatively sharp bend. It is known that redirecting fluid flow through a sharp bend develops turbulent secondary currents that result in shock and friction losses. The shock and friction losses add to the pressure drop across the reversing valve which must be compensated for by the compressor, therefore reducing the efficiency of the heat pump system.